Contributed by Aofei Li, MD and Scott Kulich, MD, PhD
A teenage girl presented to an outside facility due to headache. Her symptoms started approximately about a month and a half prior to presentation, initially being just a headache but had progressed with the patient developing nausea and vomiting. She subsequently underwent an MRI which showed a 3.5 x 3.2 cm mass lesion, with a low signal on T1 and a high signal on T2-weighted images, demonstrating a nodular thick rind of enhancement and marked surrounding vasogenic edema. The patient was taken to the operating room for resection and a 2.5 x 1.1 x 0.2 cm aggregate of tan-white to tan-red, glistening, hemorrhagic soft to rubbery tissue was received for evaluation.
H&E-stained sections revealed a relatively well circumscribed neoplasm. The neoplasm had a variable appearance ranging from more solid areas to other less cellular regions demonstrating perivascular accentuation with a pseudorosette/pseudopapillary pattern in addition to more hypocellular regions demonstrating prominent sclerosis. The tumor cells showed variable nuclear pleomorphism and contained abundant eosinophilic cytoplasm. Mitotic figures, necrosis, and endothelial proliferation were absent.
Immunohistochemical studies for GFAP and Olig2 confirmed the glial nature of the neoplasm, with GFAP stains also highlighting the relatively non-infiltrative leading edge of the neoplasm. EMA stains demonstrated dot-like reactivity in the neoplastic cells. Additional immunohistochemical stains showed a non-clonal pattern of p53 immunoreactivity and retention of nuclear staining for ATRX while stains for mutant IDH1 R132H and BRAF V600E proteins, EGFR, NeuN, and synaptophysin were interpreted as negative in the neoplastic cells. A Ki-67 stain demonstrated variable labeling of neoplastic nuclei with a proliferation index that approached 5% in the most proliferative areas.
Next generation sequencing (GlioSeq) was performed which detected a MN1/BEND2 fusion but was negative for gene mutations and copy number variations. The best match for this neoplasm on DNA methylation array studies was to CNS high grade neuroepithelial tumor with MN1 alteration (Calibrated Score 0.43; brain tumor classifier version 11b4, University of Heidelberg)